The analytical technique of x-ray energy dispersive fluorescence analysis is well known and depends fundamentally on the ability to excite, by projecting primary radiation onto a sample, and thereafter accurately to measure the characteristic K and L x-rays emanating from the sample material. The radiation from each chemical element present in the sample has an essentially unique photon energy, and the intensity of each is a function of the quantity of that element.
In chemical manufacturing operations it is often advantageous to analyze successively a multiplicity of different sample streams drawn from different points in the process, and to do this rapidly on samples which are available as continuously flowing streams piped to the common analysis site. It is also frequently advantageous to analyze for chemical elements which are present in the sample streams as either solids or in the dissolved state. For example, catalytic metals are often utilized as solids slurries and the accurate analyses of these slurries by flow of the suspensions through analytical cells is often desired.
The advent of solid-state x-ray detectors of improved resolution and increased acceptance angle, in combination with electronic pulse analyzers of improved reliability, has expanded the applicability of x-ray fluorescence analysis to a great number and variety of manufacturing processes in the chemical industry.
One of the principal advantages of solid-state detector components for energy dispersive analysis is their multi-element detection capability for a wide range of energies and their conversion to characteristic voltage signals, allowing the intensities of many characteristic x-rays to be determined simultaneously. Also, more compact excitation radiation source-sample-detector geometries are permitted, while, at the same time, minimizing the required intensity of exciting radiation.
When samples exist as flowing liquids, they must be contained during the measurements in such a way as to satisfy, as well as take full advantage of, these improved geometric criteria. A problem of particular concern is the analysis of multiple flowing liquid samples in systems sharing the use of a single source-detector, since the cost and physical arrangement of individual source-detectors for this purpose is usually prohibitive. In each instance, the surface of the sample undergoing analysis must be maintained at a relatively fixed location with respect to both the radiation source and the detector past which the liquid is moving in a flowing motion, since it is well known that any recurrent variation of the sample surface with respect to the radiation source and detector can cause significant variations in intensity. Moreover, the materials of construction of the analysis cell, including the window portion, must be such that they will not interact with the flowing sample stream nor unduly absorb the incident and emitted radiation. These and other problems are solved by a combined sampling system and x-ray detection module in accordance with this invention.